Conventionally, batteries including secondary batteries are used. A battery is configured such that an electrode assembly is accommodated in an outer case, which is made of metal such as aluminum (see JP-A-2002-117814, for example). In the battery, the electrode assembly expands due to heat generated during charging and discharging or due to environmental temperature variations. In order to prevent abnormal discharge or abnormal heat generation due to the interference between the outer case and the expanded electrode assembly from occurring, a clearance is provided between the outer case and the electrode assembly.
In recent years, in the field of electric storage devices including batteries, there is a demand for accommodating electrode assemblies as many as possible in a certain inner volume of the outer case and for reducing the volume of each electrode assembly while maintaining the power generating capacity in order to reduce the size of the electric storage device. To meet such a demand, a clearance between the electrode assembly and the outer case is designed to be narrowed to the requisite minimum that allows the electrode assembly to be brought into contact with the outer case when the electrode assembly expands. The demand of reducing the electric storage device still has not been met and further reduction in size of the electric storage device is required.